A multicast switch (MCS) is a device that combines optical switching and multiplexing to provide a colorless, directionless, and contentionless solution typically used with reconfigurable optical add/drop multiplexers (ROADMs). In a typical M×N MCS structure, where M is the number of input ports and N is the number of output ports, an optical signal can be received by any of the M input ports and delivered at any of the N output ports. In other words, the MCS is fully interconnected.
FIG. 1 shows a schematic of a known multicast switch 100. The multicast switch 100 includes a first 1×2 switch 110 and a second 1×2 switch 120. The first switch 110 can direct an input optical signal to either a first path 115a or a second path 115b, and the second 1×2 switch 120 can direct an input optical signal to either a first path 125a or a second path 125b. The multicast switch 100 also includes a first combiner 130 connected to the paths 115a and 125a and a second combiner 140 connected to the paths 115b and 125b. The first combiner 130 is connected to a first output port 135 and the second combiner 140 is connected to a second output port 145 to deliver output signals.
In operation, the multicast switch 100 can direct an input signal at the first switch 110 to the first output port 135 by directing the input signal to the first path 115a and to the second output port 145 by directing the input signal to the second path 115b. Similarly, the multicast switch 100 can direct an input signal at the second switch 120 to the first output port 135 by directing the input signal to the first path 125a and to the second output port 145 by directing the input signal to the second path 125b. 
As can be seen in FIG. 1, the switch 110 can direct an input signal to either the first path 115a or the second path 115b, but not both. This may create several issues in practice. For example, a known MCS architecture is usually based upon a head end switch and a tail end switch, and both switches need to be coordinated for path reconfiguration. In addition, an optical network using known multicast switches at the head end may only implement 1:1 protection scheme, which typically has slower restoration compared to 1+1 protection scheme.